1. Field of the Invention
The present invention relates to a thermoelectric temperature controlled device including a drawer moveable within a cabinet designed to resemble a standard household end table, such as a night stand.
2. Discussion of the Prior Art
Thermoelectric devices which can selectively maintain their contents at an elevated or reduced temperature are known in the art. Such a device traditionally contains a power supply which provides energy necessary to move electrons through energy states across a bimetallic heat sink. As the electrons move from a lower energy state to a higher energy state, a cold junction is produced. Heat absorbed at the cold side is pumped to a hot side in proportion to the current supplied. By reversing the direction of the current, and therefore the heat flow, it is possible to change from a cooling device to a heating device.
People normally keep their beverages and other food items in a refrigerator located in a kitchen because of the necessity, or simply the desire, to maintain the particular items at a reduced temperature. With such a typical arrangement, when a cooled beverage is desired, a person must travel through the house to the refrigerator in the kitchen. Under certain circumstances, it may not be convenient, or even possible, to obtain a beverage or the like from a kitchen refrigerator. It has also been known to place a mini-refrigerator in area of a household remote from a kitchen. However, such mini-refrigerator units are typically not aesthetically appealing, but rather stand out wherever they are placed.
Portable coolers could be used to store such items in potentially convenient locations, but this creates other problems. First, these passive coolers are typically only insulated boxes without any refrigeration systems and only function to maintain the difference between the internal and external temperatures. Therefore, in order to keep the contents at a reduced temperature, an additional cooling device must be used. The items could be placed in a refrigerator or freezer for a period before being placed in the cooler, or ice packs could be placed in the cooler to prolong the cooled state of the food items. Of course, non-refrigerated coolers only maintain the temperature of its contents. Because the cooler does not have any cooling device of its own, once the ice melts, or the items lose their initial cooled state, the entire cooler will cease to cool the items.
There have been developed systems for cooling using thermoelectric devices. These systems generally use a heat sink to dissipate heat from the device. In a typical heat sink arrangement, a heat generating device is provided with a number of electrically conductive fingers or fins which conduct excess heat away from the heat generating device. The excess heat is dissipated through the fingers. The amount of heat dissipated can be increased by forming the fingers with greater surface areas and/or creating an air flow across the fingers. Generally, in thermoelectric cooling devices, a fan draws air from inside a cooling chamber and blows the air across the cold side of a heat sink. Electric current flowing through the thermoelectric device causes heat to flow from the cold side to the hot side. As such, heat is extracted from the air inside the cooling chamber and drawn across the heat sink to the hot side, where the heat is dissipated.
Accordingly, small devices have been developed which actively cool their contents without bulky traditional refrigeration systems. The system described in U.S. Pat. No. 5,301,508 to Kahl et al. represents a portable container incorporating a cooling device. Essentially, the system represents a traditional passive cooler with a small removable refrigeration apparatus installed therein without any substantial air circulation apparatus. Although this system will actually cool the contents of the cooler, it is not very efficient. First, the location of the thermoelectric cooling element is on a wall adjacent to the opening. Therefore, when the cooler is opened, the fan inside the thermoelectric cooling element is drawing in ambient air. In addition, the thermoelectric unit does not efficiently distribute the cooled air throughout the chamber.
U.S. Pat. No. 3,733,836 to Corini discloses a cooling unit including an inner shell with a plurality of holes inside an associated cooling chamber. By positioning a thermoelectric device and fan between the inner shell and an outer shell, the fan distributes cooled air through the gap formed between the two shells. The cooled air then enters the cooling chamber through the holes. Although such a configuration works well for a device such as an ice cream cart, inserting a drawer into the cooling chamber would prevent adequate cooling of the chamber. Additionally, because air cannot flow across the hot side heat sink, the potential efficiency of the thermoelectric device is reduced.
Based on the above, there exists a need for an efficient thermoelectric device particularly adapted for conveniently storing and cooling food items. In addition, there exists a need for a compact thermoelectric cooling device which can be used in various environments, particularly in connection with conveniently storing food items in areas outside the kitchen.
The present invention is particularly directed to a cooling unit using a thermoelectric device with a fan to circulate cooled air throughout a cooling chamber. More specifically, a first fan is provided to draw air from the cooling chamber and blow the air across a cold side heat sink. The electric current supplied to the thermoelectric device causes the cold side heat sink to draw heat from the air and pass the absorbed heat to the hot side heat sink where it can be dissipated. The entire apparatus is preferably designed to resemble an end table, such as a nightstand, found in a typical household.
In a preferred form of the invention, a drawer is installed inside the thermoelectric cooling device. The fan blows cooled air from between an inner liner and an outer liner, and the drawer is designed to allow for the circulation of air through the drawer. In accordance with the invention, the same fan also draws air from inside the drawer, causes the air to flow over the cold side heat sink and then recycles the air back into the drawer. Specifically, the drawer is designed with various ports and openings to accommodate the desired circulation. In accordance with the most preferred form of the invention, the drawer is essentially constituted by a frame with many holes, rather than a traditional drawer having solid side walls.
The thermoelectric device is also provided with a second fan to increase system efficiency. As the first fan draws the air from inside the cooling chamber and blows the air across the cold side heat sink prior to returning the cooled air to the cooling chamber, the thermoelectric device causes absorbed heat to travel to a hot side heat sink. The second fan is located near the hot side heat sink such that the excess heat can be more quickly dissipated. With both the cold side heat sink fan and the hot side heat sink fan running, the temperature regulating efficiency of the thermoelectric device can be greatly increased.
Because the heat flow of a thermoelectric device depends upon the direction of current flow, the thermoelectric cooling drawer of the invention can also be used to heat the contents of the drawer. To change the thermoelectric device from a cooling mode to a heating mode, a switch is provided to reverse the polarity of the power supply. This causes the heat flow direction to be reversed and heat to build up on the drawer side of the thermoelectric device.
Additional objects, features and advantages of the invention will become more readily apparent from the following detailed description of a preferred embodiment thereof, when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views.